In free space optics an optical transceiver sends and receives optical signals from a second transceiver located some distance away. Alignment of the two transceivers is crucial for error free transmission of the signals exchanged between the two transceivers.
A photodetector is used in each of the transceivers to convert the optical signals to electrical signals to be processed by the electronic components of the transceiver. However, even if the transceivers are initially aligned properly, optical aberrations due to weather conditions or aging of the optical or mechanical components of the transceivers and misalignment of the transceivers due to mechanical forces from wind or other factors can lead to improper focusing of the incoming beam onto the photodetector, thus leading to errors in the transmission. Also, to detect high-speed optical signals it is necessary to use small low capacitance photodiodes, which further reduces the detection area and makes optical alignment of the receiver and transmitter difficult.
In this patent, a novel detection apparatus is introduced that uses a combination of photodetectors and transimpedance amplifiers in close proximity to reduce capacitance and distributed over a wide detection area, thus eliminating the issues related to prior art photodetectors.